Working station of a machine processing plate elements

ABSTRACT

A working station for a machine for processing plate-like elements having a front end. A working tool supported on the machine frame has a trailing end in a feed direction of the plate-like elements. A transverse gripper bar extending across the working station has at least one gripper for seizing the leading edge of the sheet. A drive device at one end of the gripper bar with two flexible drive chains at opposite ends drives the gripper bar. The gripper bar is guided down toward the downstream end of the working tool when the gripper bar crosses the downstream end of the working tool, by transverse link axles connected with the chain, to a cam sensor or follower and a lever arm between axles. A cam surface on the frame contacts the cam sensor as the gripper bar passes the end of the working station and urges the cam sensor, the lever arm and the gripper bar to swivel down toward the working tool. At the end of the cam surface, the cam sensor and the gripper bar are urged upwardly off the working surface.

BACKGROUND OF THE INVENTION

The present invention refers to a working station of a machine which processes plate elements, for example a waste stripping station of a sheet diecut into a platen press, and particularly to a redirecting guide for deflecting the sheet.

The machine comprises a frame, a working tool, for example a stripping plate, on which the sheet must be laid, a transverse gripper bar for seizing the leading edge of the sheet, two spaced apart flexible drive devices shaped like endless loops, e.g., chains, each fixedly attached to one end of the gripper bar, means, e.g., sprockets for guiding the flexible drive devices on the frame and means for bringing the gripper bar closer to the working tool when the gripper bar crosses the downstream end of the working tool.

Several solutions have already been proposed for bringing sheets conveyed by a gripper bar into contact with a stripping plate. One can divide the solutions between ones wherein the gripper bar remains on a rectilinear trajectory and the working tool, for example, the stripping plate, and particularly its leading edge only, moves toward the sheet and the other solutions wherein the gripper bar is moved closer to the working tool. Among the latter solutions, one proposes to move the chain guides and the gripper bar, where the motion is in synchronism with the control over other processing operations of the plate element, i.e. of the stripping operation. Such a solution is extremely complicated, because for moving such a unit, it is necessary to provide means for guiding cams. Moreover, the density or mass of such a movable unit causes acceleration problems limiting the machine rates and requires complicated jointed chain guides comprising control pull rods for lengthening of the chain guides, enabling the latter to follow the chains direction.

One solution proposes to obviate the above noted drawback by inserting a cam at the gripper bar ends between two chain links and by arranging a fixed roll into the cam trajectory. The length of the cam is thus limited by the one of the fastening device connecting the gripper bar to the chains having a length that is limited by the diameter of the sprocket wheels, because the acceleration of the gripper bar is very important. If the acceleration is tolerable with reference to thick cardboard sheets, namely with corrugated board, it is not tolerable for thinner and thus more delicate sheets. Since the drive chains of the gripper bars are shaped as endless loops rotating about the wheels, it is not possible to increase the length of these cams, as the cams cannot thus be longer than the chain links.

One known solution also proposes to bend the gripper bar trajectory via the chain guides shape, for bringing the gripper bar downwards to its stop end in relation to the area where the grippers of the gripper bar are at the front end of the working tool. Such a solution may cause a fault when usually guiding the chains, forcing the chains to follow the bent trajectory, not only when the gripper bar reaches its stop end at a low speed, even near to zero, but also during the whole end of the sheets traveling cycle at high speed, obviously causing wear and vibration problems.

SUMMARY OF THE INVENTION

The aim of the present invention is to obviate, at least partly, the drawbacks of the above-mentioned solutions.

To this aim, this invention concerns a working station of a machine for processing plate-like elements. Each plate-like elements has a front end. The machine includes a frame. A working tool is supported on the frame. The working tool has a trailing end in a feed direction of the plate-like elements. A transverse gripper bar extending across the working station has at least one gripper for seizing the leading edge of the sheet. There is a flexible drive device at one end of the gripper bar with two flexible drive devices at opposite ends, shaped like endless loops, e.g., a chain, to drive the gripper bar. To guide the gripper bar down toward the downstream end of the working tool when the gripper bar is crossing the downstream end of the working tool, there is at least one transverse link axle connected with the flexible drive, another link axle rearward of the first link axle and connected to a cam sensor or cam follower and a lever arm between them. A cam on the frame contacts the cam sensor as the gripper bar passes the end of the working station and urges the cam sensor, the lever arm and the gripper bar to swivel down toward the working tool. The swiveling around the front link axle temporarily brings the gripper bar and the leading edge of the sheet downward to the working tool. At the end of the cam, the cam sensor and the gripper bar are urged upwardly off the working surface. There may be two flexible drives at opposite ends of the gripper bar and the flexible drives may be chains or other endless loops.

Because of the invention, the moving masses are relatively weak. Since the lowering cam of the gripper bar is mounted on the frame of the platen press and is not mounted between two chain links, this enables appreciably increasing the length of the cam, because its length is no longer dependent on the chain link length, and that also enables reducing accelerations. The working station according to the invention can thus be used for processing thinner and less inflexible sheets than those sheets that were processed according to the prior art. Another advantage of the invention is its simplicity, which improves reliability. As noted from the following description, fitting of the devices of the working station is accurate and easy to carry out.

Further features and advantages of the invention will become evident from the following description and from the enclosed drawings illustrating, schematically and by way of example, an embodiment of the working station of a machine processing plate elements, preferably applied to a stripping station, according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the invention along the line I-I of FIG. 3;

FIG. 2 is a cross-sectional and elevational view along the line II-II of FIG. 1.

FIG. 3 is a top view along the line III-III of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT

In the following description, displacement of the gripper bar is shown by the arrow F. Since the invention particularly relates to delivering the processed sheets onto the working tool, namely the stripping plate, and does not relate to the stripping operation itself, the waste stripping and the means used for that stripping are not described or illustrated. Further, since the mechanism of a stripping device according to the invention is symmetrically arranged with respect to a longitudinal median axle of the platen press to which the stripping device is related, and that axle corresponds to the conveying direction F of the diecut sheets, only one side of the working station is shown in the drawing and is described below.

The working station illustrated in FIGS. 1 to 3 comprises the following elements. There is a frame 1 and only the part thereof located at one side of the trajectory of the sheets being processed is seen. A transverse gripper bar 2 is equipped with grippers 3 for seizing the leading edge of the sheets to be processed (not shown). Each end of the gripper bar is connected to an endless, loop type, drive chain 4 by two front link axles 5 and rear link axle 6 of the drive chain 4. Each axle is fixedly attached to a fastening piece 7 that extends on both sides of the drive chain 4. The two axles 5, 6 are mounted at both ends of the drive chain 4. The axles 5, 6 are connected to one another by the fastening piece 7 thereby forming part of an endless loop.

Since only one side of the gripper bar 2 is illustrated in the drawings, only one chain is also illustrated. The connection between the gripper bar 2 and the drive chains 4 is well-known in the art and its detailed description is not needed.

Each drive chain 4 is supported on a chain guide 8 and also wraps commonly two sprocket wheels (not shown) for that kind of machine. The drive chains 4 on which a certain tension is imparted maintain the front 5 and rear 6 link axles within an alignment with other chain links of the drive chains 4. The chains thus also are intended as pull-back means for maintaining the gripper bar 2 at an angular determined position with respect to the front 5 and rear 6 link axles. As shown in FIG. 1, at the output of the working station, where the gripper bar 2 deposits each sheet onto a stripping plate 9, the chain guide 8 comprises a short lowering ramp 8 a followed by a break of a selected length. After the end of the break, the chain guide 8 restarts with a short raising ramp 8 b.

A lowering cam 10 of the gripper bar 2 is located opposite or above the break of the chain guide 8. The cam 10 is fastened to the frame 1 by screws 11. The upper edge of the cam 10 is under a projecting part 1 a of the frame 1 (FIGS. 1 and 2).

A sensor roller 12 is like a cam follower and is fixedly attached to the gripper bar 2, preferably at each end of the gripper bar 2. That roller 12 is arranged in the vicinity of the rear link axle 6 of the drive chain 4, which connects the axle and the roller to the fastening piece 7. The piece 7 is arranged near the grippers 3 of the gripper bar 2 and the sensor roller 12.

When the sensor roller 12 which is fixedly attached to the gripper bar 2 moves under the cam 10, the roller moves the rear edge of the gripper bar 2 progressively downward. The front axle 5 is maintained by the chain guide 8, so that the gripper bar is swivelled about the front axle 5 over an angle a as shown in FIG. 1. This brings the front edge of the sheet, which has been seized by the grippers 3 of the gripper bar 2, to the level of the working tool 9.

When the cam 10 is pivoting the rear edge of the gripper bar 2, it causes an overload of the drive chains 4, while the gripper bar 2 continues its displacement into the direction of arrow F. The sensor roller 12 follows the lower edge of the cam 10, enabling the rear pivoting axle 6 to rise, and the roller 12 then meets the raising ramp 8 b of the chain guide 8 that is driving the two link axles 5, 6 between the gripper bar 2 and the drive chains 4 arranged at both ends of the gripper bar 2.

The linear cam 10, having a length in the direction F that is not limited by the driving chain links, enables limiting the acceleration of the gripper bar 2 driving its swinging motion about the front axle 5. This lengthening of the travel length of the gripper bar 2 during its lowering combines with the fact that the space between the link axles 5 and 6 connecting the drive chains 4 to the gripper bar 2 is slightly greater than the length of one link of these chains 4. Together, these increase the swivelling radius of the movable axle 6 about the fixed axle 5 that is supporting on the chain guide 8.

The means used for achieving the result are particularly simple for manufacture and for machine use and are slightly more simple than most solutions for bringing the diecut sheets onto the stripping plate. The invention, as contrasted with a solution using movable cams fixedly attached to the drive chains, is simpler and also enables reducing the accelerations imparted to the gripper bar. This would not be possible if the cam length were limited by the space between the axles of the links of the drive chain 4.

Since the drive chains are effectively traveling about sprocket wheels to enable the gripper bars to seize another sheet to achieve a new diecutting/stripping cycle, these cams length cannot be slightly greater than the length of the space between the axles of the links. However, the lowering motion of the gripper bar being constant combined with the links length, and the acceleration imparted to the gripper bar 2 by the lowering cam 10 being in relationship to the drive speed of the gripper bars, limits the drive speed and consequently the platen press rate.

The invention enables slightly increasing the time duration of the gripper bar lowering due to the appreciable increase in the length of the cam 10 with respect to cams that might be fixedly attached to the drive chains and to the fact that the space between the link axles front 5 and rear 6 connecting the gripper bar 2 to the drive chains 4 is greater than the links length. One can appreciably increase with constant speed the processing rate of the diecut sheets into the platen press with the device of the invention. According to the kind of sheets to be processed, one could to the contrary operate at a lower rate for reducing the accelerations imparted to the sheet at the time of the lowering of the gripper bar 2.

Several alternatives to the above mentioned station could be provided. The above description uses drive chains 4, which are the usual drive means for this kind of machine. One could also use any other connecting and driving means like belts, belts with driving organs, steel belts or reinforced belts, etc. Although the illustrated means for bringing back the gripper bar 2 into determined positions about the axle front 5 and rear 6 use the tension of the drive chains, other connecting devices between the gripper bar 2 and the drive chains 4 might be used as well as means separate from the chains 4 for bringing the gripper bar 2 back into a determined position about a single transverse axle fixedly attached to the chains 4. Lastly, although two lowering cams 10 are preferable, with one at each end of the gripper bar, only one cam could be arranged in the middle of the gripper bar instead of at one end.

Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims. 

1. A working station for a machine for processing plate-like elements, the working station comprising: a frame; a working tool supported on the frame and onto which a plate-like element may be arranged; a gripper bar extending transversely of the working tool and including an element for seizing the leading edge of a sheet of plate-like element as it is advanced over the working tool; a flexible drive device attached to the gripper bar for advancing the gripper bar and thereby advancing the plate-like element; a drive for the flexible drive device and supported on the frame; the gripper bar being movable toward the working tool and with respect to the flexible drive as the gripper bar crosses the downstream end of the working tool during advancing of the flexible drive and the gripper bar; at least one transverse link axle connected with the flexible drive; a cam sensor movable toward and away from the working tool; a lever arm connecting the at least one link axle with the cam sensor and the cam sensor being swivellable about the at least one link axle, a pull-back device for maintaining the lever arm and the cam sensor in a determined position about the at least one transverse link axle; a gripper bar lowering cam attached to the frame and extending in the feed direction of the plate-like element and having a cam surface placed to intersect the trajectory of the cam sensor as the flexible drive device and the cam sensor are advanced to the feed direction, the cam surface being-positioned that upon contacting the sensor cam, the cam surface swivels the cam sensor toward the working surface and swivels the gripper bar and the sensor cam about the at least one link axle for temporarily moving the gripper and the leading edge of the sheet toward the working tool.
 2. The working station of claim 1, further comprising a guide element in the feed direction of the plate-like element for contacting the cam sensor and for swiveling the cam sensor and the gripper bar back off the working tool after the cam sensor has passed the lowering cam.
 3. The working station of claim 1, wherein the at least one link axle comprises a first link axle and a second link axle, the cam sensor being swivellable about the first axle.
 4. The working station of claim 2, wherein the second axle supports the cam sensor roller.
 5. The working station of claim 4, wherein the cam sensor is a roller.
 6. The working station of claim 1, wherein the gripper bar has opposite lateral sides and the flexible drive device comprises two flexible drive devices attached at opposite ends of the gripper bar and movable together.
 7. The working station of claim 6, wherein the drive devices are shaped like endless loops guided in an endless continuous path.
 8. The working station of claim 7, wherein the drive devices are chains.
 9. The working station of claim 6, wherein: the at least one link axle comprises a first link axle and a second link axle, the cam sensor being swivellable about the first axle; the second axis supports the cam sensor roller; the flexible drive device is a chain to which the first and second link axle is attached; chain guides attached to the frame and in contact with the chain, the chain guides are shaped for enabling swiveling of the gripper bar held at the second axle around the first link axle supported on the chain guide when the cam sensor contacts the cam surface.
 10. The working station of claim 3, wherein the first link axle leads to the second link axle along the feed direction of the plate-like elements.
 11. The working station of claim 3, wherein the cam sensor is located in the vicinity of the rear link axle between the gripper bar and the chain guide. 